Spiral path based three-point turn planning for autonomous driving vehicles

ABSTRACT

In one embodiment, in response to a request to make a three-point turn for an autonomous driving vehicle (ADV), a forward turning path is generated using a first spiral function based on a maximum forward curvature change rate. A backward turning path is generated using a second spiral function based on a maximum backward curvature change rate. The forward and backward curvature change rates may be determined based on the maximum forward and backward turning angles associated with the ADV, which may be specified as a part of vehicle specification or vehicle design of the ADV. The backward turning path is initiated from an end point of the forward turning path. A three-point turn path is then generated based on the forward turning path and the backward turning path. The ADV is then driven according to the three-point turn path by issuing one or more proper control commands.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a U.S. National Phase Application under 35U.S.C. § 371 of International Application No. PCT/CN2018/108355, filedSep. 28, 2018, entitled “A SPIRAL PATH BASED THREE-POINT TURN PLANNINGFOR AUTONOMOUS DRIVING VEHICLES,” which is incorporated by referenceherein by its entirety.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to operatingautonomous vehicles. More particularly, embodiments of the disclosurerelate to techniques for planning a three-point turn of an autonomousdriving vehicle.

BACKGROUND

Vehicles operating in an autonomous mode (e.g., driverless) can relieveoccupants, especially the driver, from some driving-relatedresponsibilities. When operating in an autonomous mode, the vehicle cannavigate to various locations using onboard sensors, allowing thevehicle to travel with minimal human interaction or in some caseswithout any passengers.

Motion planning and control are critical operations in autonomousdriving. When a three-point turn is needed, for example for a U-turnwithin a road that is not wide enough to make a continuous U-turnwithout stopping and backward, a vehicle has to make a forward turningturn, in most countries, a left forward turn, towards a boundary of thelane. The vehicle then makes a backward turning turn away from theboundary. Finally, the vehicle makes a forward move to enter a targetlane. Planning such a three-point turn path is complicated. There hasbeen a lack of efficient ways to plan and control an autonomous drivingvehicle to make a three-point turn.

SUMMARY

In a first aspect, the present disclosure provides acomputer-implemented method for operating an autonomous driving vehicle,the method including in response to a request to make a three-point turnfor the autonomous driving vehicle (ADV), generating a forward turningpath using a first spiral function based on a maximum forward curvaturechange rate associated with the ADV, wherein the forward turning path isinitiated based on a current vehicle status of the ADV; generating abackward turning path using a second spiral function based on a maximumbackward curvature change rate associated with the ADV, wherein thebackward turning path is initiated from an end point of the forwardturning path; generating a three-point turn path based on the forwardturning path and the backward turning path; and issuing one or morecontrol commands to control the ADV to drive according to thethree-point turn path.

In a second aspect, the present disclosure provides a non-transitorymachine-readable medium having instructions stored therein, which whenexecuted by a processor, cause the processor to perform operations, theoperations including: in response to a request to make a three-pointturn for the autonomous driving vehicle (ADV), generating a forwardturning path using a first spiral function based on a maximum forwardcurvature change rate associated with the ADV, wherein the forwardturning path is initiated based on a current vehicle status of the ADV;generating a backward turning path using a second spiral function basedon a maximum backward curvature change rate associated with the ADV,wherein the backward turning path is initiated from an end point of theforward turning path; generating a three-point turn path based on theforward turning path and the backward turning path; and issuing one ormore control commands to control the ADV to drive according to thethree-point turn path.

In a third aspect, the disclosure provides a data processing system,including a processor; and a memory coupled to the processor to storeinstructions, which when executed by the processor, cause the processorto perform operations, the operations including in response to a requestto make a three-point turn for the autonomous driving vehicle (ADV),generating a forward turning path using a first spiral function based ona maximum forward curvature change rate associated with the ADV, whereinthe forward turning path is initiated based on a current vehicle statusof the ADV, generating a backward turning path using a second spiralfunction based on a maximum backward curvature change rate associatedwith the ADV, wherein the backward turning path is initiated from an endpoint of the forward turning path, generating a three-point turn pathbased on the forward turning path and the backward turning path, andissuing one or more control commands to control the ADV to driveaccording to the three-point turn path.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure are illustrated by way of example and notlimitation in the figures of the accompanying drawings in which likereferences indicate similar elements.

FIG. 1 is a block diagram illustrating a networked system according toone embodiment.

FIG. 2 is a block diagram illustrating an example of an autonomousvehicle according to one embodiment.

FIGS. 3A-3B are block diagrams illustrating an example of a perceptionand planning system used with an autonomous vehicle according to oneembodiment.

FIG. 4 is a diagram illustrating a three-point turn driving scenarioaccording to one embodiment.

FIG. 5 is a block diagram illustrating an example of a planning moduleaccording to one embodiment.

FIG. 6 is a flow diagram illustrating a process of generating athree-point turn path for an autonomous driving vehicle according to oneembodiment.

FIG. 7 is a block diagram illustrating a data processing systemaccording to one embodiment.

DETAILED DESCRIPTION

Various embodiments and aspects of the disclosures will be describedwith reference to details discussed below, and the accompanying drawingswill illustrate the various embodiments. The following description anddrawings are illustrative of the disclosure and are not to be construedas limiting the disclosure. Numerous specific details are described toprovide a thorough understanding of various embodiments of the presentdisclosure. However, in certain instances, well-known or conventionaldetails are not described in order to provide a concise discussion ofembodiments of the present disclosures.

Reference in the specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin conjunction with the embodiment can be included in at least oneembodiment of the disclosure. The appearances of the phrase “in oneembodiment” in various places in the specification do not necessarilyall refer to the same embodiment.

Accordingly, a free-space spiral path generated based on a spiralfunction is utilized to represent a forward turning path and a backwardturning path during a three-point turn. According to one embodiment, inresponse to a request to make a three-point turn for an autonomousdriving vehicle (ADV), a forward turning path is generated using a firstspiral function based on a maximum forward curvature change rate. Abackward turning path is generated using a second spiral function basedon a maximum backward curvature change rate. The forward and backwardcurvature change rates may be determined based on the maximum forwardand backward turning angles associated with the ADV, which may bespecified as a part of vehicle specification or vehicle design of theADV. The backward turning path is initiated from an end point of theforward turning path. A three-point turn path is then generated based onthe forward turning path and the backward turning path. The ADV is thendriven according to the three-point turn path by issuing one or moreproper control commands.

According to one embodiment, a forward straight path generated that isinitiated from an end point of the backward turning path, wherein thethree-point turn path is generated by connecting the forward turningpath, the backward turning path, and the forward straight path together.The forward straight path is generated according to a lane changingscheme from the end point of the backward turn path to drive the ADVinto a target lane.

In one embodiment, the first spiral function is configured such that foreach of the points along the forward turning path, a heading direction(θ) is determined based on an initial heading direction (a) and aninitial curvature (b) of the ADV at a starting point of the forwardspiral path. The heading direction (θ) is determined further based on adistance (s) between each point and the starting point and a maximumcurvature changing rate (c) of the ADV. In one embodiment, the headingdirection (θ) of a given point is determined according to followingequation: θ=a+b*s+c*s²/2. In one embodiment, coordinates (x, y) of agiven point along the first spiral path based on following equations:x=∫₀ ^(s) cos(θ) ds+x₀ and y=∫₀ ^(s) sin(θ) ds+y₀. Coordinate (x₀, y₀)represents an initial location of the ADV at the starting point of thefirst spiral path. The second spiral function is configured similar tothe first spiral function.

FIG. 1 is a block diagram illustrating an autonomous vehicle networkconfiguration according to one embodiment of the disclosure. Referringto FIG. 1, network configuration 100 includes autonomous vehicle 101that may be communicatively coupled to one or more servers 103-104 overa network 102. Although there is one autonomous vehicle shown, multipleautonomous vehicles can be coupled to each other and/or coupled toservers 103-104 over network 102. Network 102 may be any type ofnetworks such as a local area network (LAN), a wide area network (WAN)such as the Internet, a cellular network, a satellite network, or acombination thereof, wired or wireless. Server(s) 103-104 may be anykind of servers or a cluster of servers, such as Web or cloud servers,application servers, backend servers, or a combination thereof. Servers103-104 may be data analytics servers, content servers, trafficinformation servers, map and point of interest (MPOI) servers, orlocation servers, etc.

An autonomous vehicle refers to a vehicle that can be configured to inan autonomous mode in which the vehicle navigates through an environmentwith little or no input from a driver. Such an autonomous vehicle caninclude a sensor system having one or more sensors that are configuredto detect information about the environment in which the vehicleoperates. The vehicle and its associated controller(s) use the detectedinformation to navigate through the environment. Autonomous vehicle 101can operate in a manual mode, a full autonomous mode, or a partialautonomous mode.

In one embodiment, autonomous vehicle 101 includes, but is not limitedto, perception and planning system 110, vehicle control system 111,wireless communication system 112, user interface system 113,infotainment system 114, and sensor system 115. Autonomous vehicle 101may further include certain common components included in ordinaryvehicles, such as, an engine, wheels, steering wheel, transmission,etc., which may be controlled by vehicle control system 111 and/orperception and planning system 110 using a variety of communicationsignals and/or commands, such as, for example, acceleration signals orcommands, deceleration signals or commands, steering signals orcommands, braking signals or commands, etc.

Components 110-115 may be communicatively coupled to each other via aninterconnect, a bus, a network, or a combination thereof. For example,components 110-115 may be communicatively coupled to each other via acontroller area network (CAN) bus. A CAN bus is a vehicle bus standarddesigned to allow microcontrollers and devices to communicate with eachother in applications without a host computer. It is a message-basedprotocol, designed originally for multiplex electrical wiring withinautomobiles, but is also used in many other contexts.

Referring now to FIG. 2, in one embodiment, sensor system 115 includes,but it is not limited to, one or more cameras 211, global positioningsystem (GPS) unit 212, inertial measurement unit (IMU) 213, radar unit214, and a light detection and range (LIDAR) unit 215. GPS system 212may include a transceiver operable to provide information regarding theposition of the autonomous vehicle. IMU unit 213 may sense position andorientation changes of the autonomous vehicle based on inertialacceleration. Radar unit 214 may represent a system that utilizes radiosignals to sense objects within the local environment of the autonomousvehicle. In some embodiments, in addition to sensing objects, radar unit214 may additionally sense the speed and/or heading of the objects.LIDAR unit 215 may sense objects in the environment in which theautonomous vehicle is located using lasers. LIDAR unit 215 could includeone or more laser sources, a laser scanner, and one or more detectors,among other system components. Cameras 211 may include one or moredevices to capture images of the environment surrounding the autonomousvehicle. Cameras 211 may be still cameras and/or video cameras. A cameramay be mechanically movable, for example, by mounting the camera on arotating and/or tilting a platform.

Sensor system 115 may further include other sensors, such as, a sonarsensor, an infrared sensor, a steering sensor, a throttle sensor, abraking sensor, and an audio sensor (e.g., microphone). An audio sensormay be configured to capture sound from the environment surrounding theautonomous vehicle. A steering sensor may be configured to sense thesteering angle of a steering wheel, wheels of the vehicle, or acombination thereof. A throttle sensor and a braking sensor sense thethrottle position and braking position of the vehicle, respectively. Insome situations, a throttle sensor and a braking sensor may beintegrated as an integrated throttle/braking sensor.

In one embodiment, vehicle control system 111 includes, but is notlimited to, steering unit 201, throttle unit 202 (also referred to as anacceleration unit), and braking unit 203. Steering unit 201 is to adjustthe direction or heading of the vehicle. Throttle unit 202 is to controlthe speed of the motor or engine that in turn control the speed andacceleration of the vehicle. Braking unit 203 is to decelerate thevehicle by providing friction to slow the wheels or tires of thevehicle. Note that the components as shown in FIG. 2 may be implementedin hardware, software, or a combination thereof.

Referring back to FIG. 1, wireless communication system 112 is to allowcommunication between autonomous vehicle 101 and external systems, suchas devices, sensors, other vehicles, etc. For example, wirelesscommunication system 112 can wirelessly communicate with one or moredevices directly or via a communication network, such as servers 103-104over network 102. Wireless communication system 112 can use any cellularcommunication network or a wireless local area network (WLAN), e.g.,using WiFi to communicate with another component or system. Wirelesscommunication system 112 could communicate directly with a device (e.g.,a mobile device of a passenger, a display device, a speaker withinvehicle 101), for example, using an infrared link, Bluetooth, etc. Userinterface system 113 may be part of peripheral devices implementedwithin vehicle 101 including, for example, a keyboard, a touch screendisplay device, a microphone, and a speaker, etc.

Some or all of the functions of autonomous vehicle 101 may be controlledor managed by perception and planning system 110, especially whenoperating in an autonomous driving mode. Perception and planning system110 includes the necessary hardware (e.g., processor(s), memory,storage) and software (e.g., operating system, planning and routingprograms) to receive information from sensor system 115, control system111, wireless communication system 112, and/or user interface system113, process the received information, plan a route or path from astarting point to a destination point, and then drive vehicle 101 basedon the planning and control information. Alternatively, perception andplanning system 110 may be integrated with vehicle control system 111.

For example, a user as a passenger may specify a starting location and adestination of a trip, for example, via a user interface. Perception andplanning system 110 obtains the trip related data. For example,perception and planning system 110 may obtain location and routeinformation from an MPOI server, which may be a part of servers 103-104.The location server provides location services and the MPOI serverprovides map services and the POIs of certain locations. Alternatively,such location and MPOI information may be cached locally in a persistentstorage device of perception and planning system 110.

While autonomous vehicle 101 is moving along the route, perception andplanning system 110 may also obtain real-time traffic information from atraffic information system or server (TIS). Note that servers 103-104may be operated by a third party entity. Alternatively, thefunctionalities of servers 103-104 may be integrated with perception andplanning system 110. Based on the real-time traffic information, MPOIinformation, and location information, as well as real-time localenvironment data detected or sensed by sensor system 115 (e.g.,obstacles, objects, nearby vehicles), perception and planning system 110can plan an optimal route and drive vehicle 101, for example, viacontrol system 111, according to the planned route to reach thespecified destination safely and efficiently.

Server 103 may be a data analytics system to perform data analyticsservices for a variety of clients. In one embodiment, data analyticssystem 103 includes data collector 121 and machine learning engine 122.Data collector 121 collects driving statistics 123 from a variety ofvehicles, either autonomous vehicles or regular vehicles driven by humandrivers. Driving statistics 123 include information indicating thedriving commands (e.g., throttle, brake, steering commands) issued andresponses of the vehicles (e.g., speeds, accelerations, decelerations,directions) captured by sensors of the vehicles at different points intime. Driving statistics 123 may further include information describingthe driving environments at different points in time, such as, forexample, routes (including starting and destination locations), MPOIs,road conditions, weather conditions, etc.

Based on driving statistics 123, machine learning engine 122 generatesor trains a set of rules, algorithms, and/or predictive models 124 for avariety of purposes. In one embodiment, algorithms 124 may includedefining and configuring a first spiral function for generating aforward turning path and a second spiral function for generating abackward turning path. Algorithms 124 can then be uploaded on ADVs to beutilized during autonomous driving in real-time.

FIGS. 3A and 3B are block diagrams illustrating an example of aperception and planning system used with an autonomous vehicle accordingto one embodiment. System 300 may be implemented as a part of autonomousvehicle 101 of FIG. 1 including, but is not limited to, perception andplanning system 110, control system 111, and sensor system 115.Referring to FIGS. 3A-3B, perception and planning system 110 includes,but is not limited to, localization module 301, perception module 302,prediction module 303, decision module 304, planning module 305, controlmodule 306, and routing module 307.

Some or all of modules 301-307 may be implemented in software, hardware,or a combination thereof. For example, these modules may be installed inpersistent storage device 352, loaded into memory 351, and executed byone or more processors (not shown). Note that some or all of thesemodules may be communicatively coupled to or integrated with some or allmodules of vehicle control system 111 of FIG. 2. Some of modules 301-307may be integrated together as an integrated module.

Localization module 301 determines a current location of autonomousvehicle 300 (e.g., leveraging GPS unit 212) and manages any data relatedto a trip or route of a user. Localization module 301 (also referred toas a map and route module) manages any data related to a trip or routeof a user. A user may log in and specify a starting location and adestination of a trip, for example, via a user interface. Localizationmodule 301 communicates with other components of autonomous vehicle 300,such as map and route information 311, to obtain the trip related data.For example, localization module 301 may obtain location and routeinformation from a location server and a map and POI (MPOI) server. Alocation server provides location services and an MPOI server providesmap services and the POIs of certain locations, which may be cached aspart of map and route information 311. While autonomous vehicle 300 ismoving along the route, localization module 301 may also obtainreal-time traffic information from a traffic information system orserver.

Based on the sensor data provided by sensor system 115 and localizationinformation obtained by localization module 301, a perception of thesurrounding environment is determined by perception module 302. Theperception information may represent what an ordinary driver wouldperceive surrounding a vehicle in which the driver is driving. Theperception can include the lane configuration, traffic light signals, arelative position of another vehicle, a pedestrian, a building,crosswalk, or other traffic related signs (e.g., stop signs, yieldsigns), etc., for example, in a form of an object. The laneconfiguration includes information describing a lane or lanes, such as,for example, a shape of the lane (e.g., straight or curvature), a widthof the lane, how many lanes in a road, one-way or two-way lane, mergingor splitting lanes, exiting lane, etc.

Perception module 302 may include a computer vision system orfunctionalities of a computer vision system to process and analyzeimages captured by one or more cameras in order to identify objectsand/or features in the environment of autonomous vehicle. The objectscan include traffic signals, road way boundaries, other vehicles,pedestrians, and/or obstacles, etc. The computer vision system may usean object recognition algorithm, video tracking, and other computervision techniques. In some embodiments, the computer vision system canmap an environment, track objects, and estimate the speed of objects,etc. Perception module 302 can also detect objects based on othersensors data provided by other sensors such as a radar and/or LIDAR.

For each of the objects, prediction module 303 predicts what the objectwill behave under the circumstances. The prediction is performed basedon the perception data perceiving the driving environment at the pointin time in view of a set of map/rout information 311 and traffic rules312. For example, if the object is a vehicle at an opposing directionand the current driving environment includes an intersection, predictionmodule 303 will predict whether the vehicle will likely move straightforward or make a turn. If the perception data indicates that theintersection has no traffic light, prediction module 303 may predictthat the vehicle may have to fully stop prior to enter the intersection.If the perception data indicates that the vehicle is currently at aleft-turn only lane or a right-turn only lane, prediction module 303 maypredict that the vehicle will more likely make a left turn or right turnrespectively.

For each of the objects, decision module 304 makes a decision regardinghow to handle the object. For example, for a particular object (e.g.,another vehicle in a crossing route) as well as its metadata describingthe object (e.g., a speed, direction, turning angle), decision module304 decides how to encounter the object (e.g., overtake, yield, stop,pass). Decision module 304 may make such decisions according to a set ofrules such as traffic rules or driving rules 312, which may be stored inpersistent storage device 352.

Routing module 307 is configured to provide one or more routes or pathsfrom a starting point to a destination point. For a given trip from astart location to a destination location, for example, received from auser, routing module 307 obtains route and map information 311 anddetermines all possible routes or paths from the starting location toreach the destination location. Routing module 307 may generate areference line in a form of a topographic map for each of the routes itdetermines from the starting location to reach the destination location.A reference line refers to an ideal route or path without anyinterference from others such as other vehicles, obstacles, or trafficcondition. That is, if there is no other vehicle, pedestrians, orobstacles on the road, an ADV should exactly or closely follows thereference line. The topographic maps are then provided to decisionmodule 304 and/or planning module 305. Decision module 304 and/orplanning module 305 examine all of the possible routes to select andmodify one of the most optimal route in view of other data provided byother modules such as traffic conditions from localization module 301,driving environment perceived by perception module 302, and trafficcondition predicted by prediction module 303. The actual path or routefor controlling the ADV may be close to or different from the referenceline provided by routing module 307 dependent upon the specific drivingenvironment at the point in time.

Based on a decision for each of the objects perceived, planning module305 plans a path or route for the autonomous vehicle, as well as drivingparameters (e.g., distance, speed, and/or turning angle), using areference line provided by routing module 307 as a basis. That is, for agiven object, decision module 304 decides what to do with the object,while planning module 305 determines how to do it. For example, for agiven object, decision module 304 may decide to pass the object, whileplanning module 305 may determine whether to pass on the left side orright side of the object. Planning and control data is generated byplanning module 305 including information describing how vehicle 300would move in a next moving cycle (e.g., next route/path segment). Forexample, the planning and control data may instruct vehicle 300 to move10 meters at a speed of 30 mile per hour (mph), then change to a rightlane at the speed of 25 mph.

Based on the planning and control data, control module 306 controls anddrives the autonomous vehicle, by sending proper commands or signals tovehicle control system 111, according to a route or path defined by theplanning and control data. The planning and control data includesufficient information to drive the vehicle from a first point to asecond point of a route or path using appropriate vehicle settings ordriving parameters (e.g., throttle, braking, steering commands) atdifferent points in time along the path or route.

In one embodiment, the planning phase is performed in a number ofplanning cycles, also referred to as driving cycles, such as, forexample, in every time interval of 100 milliseconds (ms). For each ofthe planning cycles or driving cycles, one or more control commands willbe issued based on the planning and control data. That is, for every 100ms, planning module 305 plans a next route segment or path segment, forexample, including a target position and the time required for the ADVto reach the target position. Alternatively, planning module 305 mayfurther specify the specific speed, direction, and/or steering angle,etc. In one embodiment, planning module 305 plans a route segment orpath segment for the next predetermined period of time such as 5seconds. For each planning cycle, planning module 305 plans a targetposition for the current cycle (e.g., next 5 seconds) based on a targetposition planned in a previous cycle. Control module 306 then generatesone or more control commands (e.g., throttle, brake, steering controlcommands) based on the planning and control data of the current cycle.

Note that decision module 304 and planning module 305 may be integratedas an integrated module. Decision module 304/planning module 305 mayinclude a navigation system or functionalities of a navigation system todetermine a driving path for the autonomous vehicle. For example, thenavigation system may determine a series of speeds and directionalheadings to affect movement of the autonomous vehicle along a path thatsubstantially avoids perceived obstacles while generally advancing theautonomous vehicle along a roadway-based path leading to an ultimatedestination. The destination may be set according to user inputs viauser interface system 113. The navigation system may update the drivingpath dynamically while the autonomous vehicle is in operation. Thenavigation system can incorporate data from a GPS system and one or moremaps so as to determine the driving path for the autonomous vehicle.

FIG. 4 shows a typical driving scenario to make a three-point turn.Referring to FIG. 4, when vehicle 400 attempts to make a three-pointturn, vehicle 400 would move to make a left turn according to forwardturning path 401 towards lane boundary 411 of lane 410. In mostjurisdictions where vehicles are driving on the right side of the road,the forward turning path 401 would be a left forward turning path.Vehicle 400 then moves backwardly according to backward turning path 402(e.g., a right backward turning path) towards lane boundary 412.Thereafter, vehicle 400 moves substantially straight forward path 403 toenter the target lane to complete the three-point turn.

FIG. 5 is a block diagram illustrating an example of a planning moduleaccording to one embodiment. Referring to FIG. 5, planning module 305includes, but it not limited to, forward turning (FT) path generator501, backward turning (BT) path generator 502, three-point turn (TT)path generator 503, which may be implemented in software, hardware, or acombination thereof. For example, modules 501-503 may be loaded into amemory and executed by one or more processors (not shown). FT pathgenerator 501 is responsible for generating one or more FT paths using afirst spiral function based on maximum FT turning angle 511 associatedwith the vehicle. The maximum FT turning angle also determines themaximum forward curvature change rate associated with the vehicle whenthe vehicle makes the sharpest forward turn. BT generator 502 isresponsible for generating one or more BT paths using a second spiralfunction based on maximum BT angle 512 associated with the vehicle.Maximum BT turning angle also determines the maximum backward curvaturechange rate when the vehicle makes the sharpest backward turn. TT pathgenerator 503 is responsible for generating a TT path based on the FTpaths and BT paths generated by FT path generator 501 and BT pathgenerator 502. Planning module 305 further includes a speed profilegenerator 504 to generate a speed profile for the selected three-pointturn path in view of the perception information describing the drivingenvironment surrounding the vehicle.

Referring now to FIGS. 4 and 5, according to one embodiment, in responseto a request to make a three-point turn for an ADV, FT path generator501 generates forward turning path 401 using a first spiral functionobtained as part of spiral functions 314 based on a maximum forwardcurvature change rate or maximum forward turning angle 511 associatedwith the ADV. BT path generator generates backward turning path 402using a second spiral function (also obtained as part of spiralfunctions 314) based on maximum backward curvature change rate ormaximum backward turning angle 512. The forward and backward curvaturechange rates may be determined based on the maximum forward and backwardturning angles associated with the ADV. The maximum forward and backwardturning angles 511-512 may be specified as a part of vehiclespecification or vehicle design of the ADV. The backward turning path isinitiated from an end point of the forward turning path. Three-pointturn path generator 503 generates a three-point turn path based on theforward turning path and the backward turning path. Based on thethree-point turn path, speed profile generator 504 generates a speedprofile for the three-point turn path. The speed profile includesinformation describing speed and heading direction of the path pointsalong the three-point turn path. The ADV is then driven according to thethree-point turn path by issuing one or more proper control commandssuch as steering, throttle, brake commands.

According to one embodiment, a forward straight path generated initiatedfrom an end point of the backward turning path, wherein the three-pointturn path is generated by connecting the forward turning path, thebackward turning path, and the forward straight path together. Theforward straight path is generated according to a lane changing schemefrom the end point of the backward turn path to drive the ADV into atarget lane.

In one embodiment, the first spiral function is configured such that foreach of the points along the forward turning path, a heading direction(θ) is determined based on an initial heading direction (a) and aninitial curvature (b) of the ADV at a starting point of the forwardspiral path. The heading direction (θ) is determined further based on adistance (s) between each point and the starting point and a maximumcurvature changing rate (c) of the ADV. In one embodiment, the headingdirection (θ) of a given point is determined according to followingequation: θ=a+b*s+c*s²/2. In one embodiment, coordinates (x, y) of agiven point along the first spiral path based on following equations:x=∫₀ ^(s) cos(θ) ds+x₀ and y=∫₀ ^(s) sin(θ) ds+y₀. Coordinate (x₀, y₀)represents an initial location of the ADV at the starting point of thefirst spiral path. The second spiral function is configured similar tothe first spiral function.

Based on the above formulas, for any given path point in a forwardturning path, its heading and coordinates can be determined based on thefollowing set of equations:θ=a+b*s+c*s ²/2x=∫ ₀ ^(s) cos(θ)ds+x ₀y=∫ ₀ ^(s) sin(θ)ds+y ₀subject to a set of constraints. The set of constraints includes 1) thecurvature dθ<curvature limit of the path; and 2) coordinate (x, y) iswithin the lane boundary.

The curvature limit refers to the maximum forward turning angle or themaximum forward curvature associated with the vehicle, which may be partof design specification of the vehicle. The lane boundary can bedetermined based on perception information perceiving a drivingenvironment surrounding the vehicle. For a forward turning path, (x₀,y₀) represents the current location of the vehicle before making athree-point turn. Variable s represents the distance along the forwardturning path between the original location (x₀, y₀) and thecorresponding path point (x, y).

The above set of equations can also be utilized to derive a backwardturning path, except that the original point or the starting point ofthe path (x₀, y₀) is the end point of the forward turning path. For abackward turning path, the curvature limit refers to the maximumbackward turning angle or the maximum backward curvature associated withthe vehicle, which may be part of design specification of the vehicle.Note that the maximum forward and backward turning angles may bedifferent for a particular vehicle. For example, the maximum forwardturning angle may be 30 degrees, while the maximum backward turningangle may be 40 degrees for a particular vehicle. Similarly, the maximumforward and backward curvatures or curvature change rates may bedifferent. The lane boundary can be determined based on perceptioninformation perceiving a driving environment surrounding the vehicle.Variable s represents the distance along the backward turning pathbetween the original location (x₀, y₀) of the backward turning path(e.g., the end point of the forward turning path) and the correspondingpath point (x, y) on the backward turning path.

FIG. 6 is a flow diagram illustrating an example of a process forgenerating a three-point turn for an autonomous driving vehicleaccording to one embodiment. Process 600 may be performed by processinglogic which may include software, hardware, or a combination thereof.For example, process 600 may be performed by planning module 305.Referring to FIG. 6, in operation 601, processing logic receives arequest to make a three-point turn of an ADV. In response, in operation602, processing logic generates a forward turning path using a firstspiral function based on the maximum forward turning angle or maximumforward curvature change rate associated with the ADV. The forwardturning path extends towards the opposing lane boundary until it reacheswithin a predetermined proximity. In operation 603, processing logicgenerates a backward turning path using a second spiral function basedon the maximum backward turning angle or maximum backward curvaturechange rate associated with the ADV. The backward turning path isinitiated from the end point of the forward turning path. The backwardturning path extends towards the other lane boundary until it reaches apredetermined proximity from the lane boundary or the heading directionis within the expected range. In operation 604, processing logicgenerates a forward straight path from the end point of the backwardturning path. The forward straight path allows the vehicle entering thetarget lane, for example, using a lane changing scheme. In operation605, processing logic generates a three-point turn path based on theforward turning path, the backward turning path, and the forwardstraight path. Thereafter, the vehicle is driven to make a three-pointturn according to the three-point turn path.

Note that some or all of the components as shown and described above maybe implemented in software, hardware, or a combination thereof. Forexample, such components can be implemented as software installed andstored in a persistent storage device, which can be loaded and executedin a memory by a processor (not shown) to carry out the processes oroperations described throughout this application. Alternatively, suchcomponents can be implemented as executable code programmed or embeddedinto dedicated hardware such as an integrated circuit (e.g., anapplication specific IC or ASIC), a digital signal processor (DSP), or afield programmable gate array (FPGA), which can be accessed via acorresponding driver and/or operating system from an application.Furthermore, such components can be implemented as specific hardwarelogic in a processor or processor core as part of an instruction setaccessible by a software component via one or more specificinstructions.

FIG. 7 is a block diagram illustrating an example of a data processingsystem which may be used with one embodiment of the disclosure. Forexample, system 1500 may represent any of data processing systemsdescribed above performing any of the processes or methods describedabove, such as, for example, perception and planning system 110 or anyof servers 103-104 of FIG. 1. System 1500 can include many differentcomponents. These components can be implemented as integrated circuits(ICs), portions thereof, discrete electronic devices, or other modulesadapted to a circuit board such as a motherboard or add-in card of thecomputer system, or as components otherwise incorporated within achassis of the computer system.

Note also that system 1500 is intended to show a high level view of manycomponents of the computer system. However, it is to be understood thatadditional components may be present in certain implementations andfurthermore, different arrangement of the components shown may occur inother implementations. System 1500 may represent a desktop, a laptop, atablet, a server, a mobile phone, a media player, a personal digitalassistant (PDA), a Smartwatch, a personal communicator, a gaming device,a network router or hub, a wireless access point (AP) or repeater, aset-top box, or a combination thereof. Further, while only a singlemachine or system is illustrated, the term “machine” or “system” shallalso be taken to include any collection of machines or systems thatindividually or jointly execute a set (or multiple sets) of instructionsto perform any one or more of the methodologies discussed herein.

In one embodiment, system 1500 includes processor 1501, memory 1503, anddevices 1505-1508 connected via a bus or an interconnect 1510. Processor1501 may represent a single processor or multiple processors with asingle processor core or multiple processor cores included therein.Processor 1501 may represent one or more general-purpose processors suchas a microprocessor, a central processing unit (CPU), or the like. Moreparticularly, processor 1501 may be a complex instruction set computing(CISC) microprocessor, reduced instruction set computing (RISC)microprocessor, very long instruction word (VLIW) microprocessor, orprocessor implementing other instruction sets, or processorsimplementing a combination of instruction sets. Processor 1501 may alsobe one or more special-purpose processors such as an applicationspecific integrated circuit (ASIC), a cellular or baseband processor, afield programmable gate array (FPGA), a digital signal processor (DSP),a network processor, a graphics processor, a communications processor, acryptographic processor, a co-processor, an embedded processor, or anyother type of logic capable of processing instructions.

Processor 1501, which may be a low power multi-core processor socketsuch as an ultra-low voltage processor, may act as a main processingunit and central hub for communication with the various components ofthe system. Such processor can be implemented as a system on chip (SoC).Processor 1501 is configured to execute instructions for performing theoperations and steps discussed herein. System 1500 may further include agraphics interface that communicates with optional graphics subsystem1504, which may include a display controller, a graphics processor,and/or a display device.

Processor 1501 may communicate with memory 1503, which in one embodimentcan be implemented via multiple memory devices to provide for a givenamount of system memory. Memory 1503 may include one or more volatilestorage (or memory) devices such as random access memory (RAM), dynamicRAM (DRAM), synchronous DRAM (SDRAM), static RAM (SRAM), or other typesof storage devices. Memory 1503 may store information includingsequences of instructions that are executed by processor 1501, or anyother device. For example, executable code and/or data of a variety ofoperating systems, device drivers, firmware (e.g., input output basicsystem or BIOS), and/or applications can be loaded in memory 1503 andexecuted by processor 1501. An operating system can be any kind ofoperating systems, such as, for example, Robot Operating System (ROS),Windows® operating system from Microsoft®, Mac OS®/iOS® from Apple,Android® from Google®, LINUX, UNIX, or other real-time or embeddedoperating systems.

System 1500 may further include IO devices such as devices 1505-1508,including network interface device(s) 1505, optional input device(s)1506, and other optional IO device(s) 1507. Network interface device1505 may include a wireless transceiver and/or a network interface card(NIC). The wireless transceiver may be a WiFi transceiver, an infraredtransceiver, a Bluetooth transceiver, a WiMax transceiver, a wirelesscellular telephony transceiver, a satellite transceiver (e.g., a globalpositioning system (GPS) transceiver), or other radio frequency (RF)transceivers, or a combination thereof. The NIC may be an Ethernet card.

Input device(s) 1506 may include a mouse, a touch pad, a touch sensitivescreen (which may be integrated with display device 1504), a pointerdevice such as a stylus, and/or a keyboard (e.g., physical keyboard or avirtual keyboard displayed as part of a touch sensitive screen). Forexample, input device 1506 may include a touch screen controller coupledto a touch screen. The touch screen and touch screen controller can, forexample, detect contact and movement or break thereof using any of aplurality of touch sensitivity technologies, including but not limitedto capacitive, resistive, infrared, and surface acoustic wavetechnologies, as well as other proximity sensor arrays or other elementsfor determining one or more points of contact with the touch screen.

TO devices 1507 may include an audio device. An audio device may includea speaker and/or a microphone to facilitate voice-enabled functions,such as voice recognition, voice replication, digital recording, and/ortelephony functions. Other IO devices 1507 may further include universalserial bus (USB) port(s), parallel port(s), serial port(s), a printer, anetwork interface, a bus bridge (e.g., a PCI-PCI bridge), sensor(s)(e.g., a motion sensor such as an accelerometer, gyroscope, amagnetometer, a light sensor, compass, a proximity sensor, etc.), or acombination thereof. Devices 1507 may further include an imagingprocessing subsystem (e.g., a camera), which may include an opticalsensor, such as a charged coupled device (CCD) or a complementarymetal-oxide semiconductor (CMOS) optical sensor, utilized to facilitatecamera functions, such as recording photographs and video clips. Certainsensors may be coupled to interconnect 1510 via a sensor hub (notshown), while other devices such as a keyboard or thermal sensor may becontrolled by an embedded controller (not shown), dependent upon thespecific configuration or design of system 1500.

To provide for persistent storage of information such as data,applications, one or more operating systems and so forth, a mass storage(not shown) may also couple to processor 1501. In various embodiments,to enable a thinner and lighter system design as well as to improvesystem responsiveness, this mass storage may be implemented via a solidstate device (SSD). However in other embodiments, the mass storage mayprimarily be implemented using a hard disk drive (HDD) with a smalleramount of SSD storage to act as a SSD cache to enable non-volatilestorage of context state and other such information during power downevents so that a fast power up can occur on re-initiation of systemactivities. Also a flash device may be coupled to processor 1501, e.g.,via a serial peripheral interface (SPI). This flash device may providefor non-volatile storage of system software, including BIOS as well asother firmware of the system.

Storage device 1508 may include computer-accessible storage medium 1509(also known as a machine-readable storage medium or a computer-readablemedium) on which is stored one or more sets of instructions or software(e.g., module, unit, and/or logic 1528) embodying any one or more of themethodologies or functions described herein. Processingmodule/unit/logic 1528 may represent any of the components describedabove, such as, for example, planning module 305, control module 306.Processing module/unit/logic 1528 may also reside, completely or atleast partially, within memory 1503 and/or within processor 1501 duringexecution thereof by data processing system 1500, memory 1503 andprocessor 1501 also constituting machine-accessible storage media.Processing module/unit/logic 1528 may further be transmitted or receivedover a network via network interface device 1505.

Computer-readable storage medium 1509 may also be used to store the somesoftware functionalities described above persistently. Whilecomputer-readable storage medium 1509 is shown in an exemplaryembodiment to be a single medium, the term “computer-readable storagemedium” should be taken to include a single medium or multiple media(e.g., a centralized or distributed database, and/or associated cachesand servers) that store the one or more sets of instructions. The terms“computer-readable storage medium” shall also be taken to include anymedium that is capable of storing or encoding a set of instructions forexecution by the machine and that cause the machine to perform any oneor more of the methodologies of the present disclosure. The term“computer-readable storage medium” shall accordingly be taken toinclude, but not be limited to, solid-state memories, and optical andmagnetic media, or any other non-transitory machine-readable medium.

Processing module/unit/logic 1528, components and other featuresdescribed herein can be implemented as discrete hardware components orintegrated in the functionality of hardware components such as ASICS,FPGAs, DSPs or similar devices. In addition, processingmodule/unit/logic 1528 can be implemented as firmware or functionalcircuitry within hardware devices. Further, processing module/unit/logic1528 can be implemented in any combination hardware devices and softwarecomponents.

Note that while system 1500 is illustrated with various components of adata processing system, it is not intended to represent any particulararchitecture or manner of interconnecting the components; as suchdetails are not germane to embodiments of the present disclosure. Itwill also be appreciated that network computers, handheld computers,mobile phones, servers, and/or other data processing systems which havefewer components or perhaps more components may also be used withembodiments of the disclosure.

Some portions of the preceding detailed descriptions have been presentedin terms of algorithms and symbolic representations of operations ondata bits within a computer memory. These algorithmic descriptions andrepresentations are the ways used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of operations leading to adesired result. The operations are those requiring physicalmanipulations of physical quantities.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the above discussion, itis appreciated that throughout the description, discussions utilizingterms such as those set forth in the claims below, refer to the actionand processes of a computer system, or similar electronic computingdevice, that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission or display devices.

Embodiments of the disclosure also relate to an apparatus for performingthe operations herein. Such a computer program is stored in anon-transitory computer readable medium. A machine-readable mediumincludes any mechanism for storing information in a form readable by amachine (e.g., a computer). For example, a machine-readable (e.g.,computer-readable) medium includes a machine (e.g., a computer) readablestorage medium (e.g., read only memory (“ROM”), random access memory(“RAM”), magnetic disk storage media, optical storage media, flashmemory devices).

The processes or methods depicted in the preceding figures may beperformed by processing logic that comprises hardware (e.g. circuitry,dedicated logic, etc.), software (e.g., embodied on a non-transitorycomputer readable medium), or a combination of both. Although theprocesses or methods are described above in terms of some sequentialoperations, it should be appreciated that some of the operationsdescribed may be performed in a different order. Moreover, someoperations may be performed in parallel rather than sequentially.

Embodiments of the present disclosure are not described with referenceto any particular programming language. It will be appreciated that avariety of programming languages may be used to implement the teachingsof embodiments of the disclosure as described herein.

In the foregoing specification, embodiments of the disclosure have beendescribed with reference to specific exemplary embodiments thereof. Itwill be evident that various modifications may be made thereto withoutdeparting from the broader spirit and scope of the disclosure as setforth in the following claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

What is claimed is:
 1. A computer-implemented method for operating anautonomous driving vehicle (ADV), the method comprising: in response toa request to make a three-point turn for the ADV, generating a forwardturning path using a first spiral function based on a maximum forwardcurvature change rate associated with the ADV, wherein the forwardturning path is initiated based on a current vehicle status of the ADV,wherein coordinates (x, y) of any given point along the forward turningpath is within a lane boundary of a current lane based on perceptioninformation perceiving a driving environment surrounding the ADV;generating a backward turning path using a second spiral function basedon a maximum backward curvature change rate associated with the ADV,wherein the backward turning path is initiated from an end point of theforward turning path; generating a three-point turn path based on theforward turning path and the backward turning path; and issuing one ormore control commands to control the ADV to drive according to thethree-point turn path.
 2. The computer-implemented method of claim 1,wherein the first spiral function is configured such that, for each of aplurality of points along the forward turning path, a heading direction(θ) is determined based on an initial heading direction (a) and aninitial curvature (b) of the ADV at a starting point of the forwardturning path.
 3. The computer-implemented method of claim 2, wherein theheading direction (θ) is determined further based on a distance (s)between each point and the starting point and a maximum curvature changerate (c) of the ADV.
 4. The computer-implemented method of claim 3,wherein the heading direction (θ) of a given point is determinedaccording to following equation: θ=a+b*s+c*s²/2.
 5. Thecomputer-implemented method of claim 4, wherein a curvature representedby a derivative of the heading direction (dθ) of any given point is lessthan a maximum curvature associated with the ADV.
 6. Thecomputer-implemented method of claim 3, wherein coordinates (x, y) of agiven point along the forward turning path are based on followingequations: x=∫₀ ^(s) cos(θ) ds+x₀ and y=∫₀ ^(s) sin(θ) ds+y₀, whereincoordinate (x₀, y₀) represents an initial location of the ADV at thestarting point of the first forward turning path.
 7. Thecomputer-implemented method of claim 1, further comprising generating aforward straight path initiated from an end point of the backwardturning path, wherein the three-point turn path is generated byconnecting the forward turning path, the backward turning path, and theforward straight path together.
 8. The computer-implemented method ofclaim 7, wherein the forward straight path is generated according to alane changing scheme from the end point of the backward turning path todrive the ADV into a target lane.
 9. A non-transitory machine-readablemedium having instructions stored therein, which when executed by aprocessor, cause the processor to perform operations, the operationscomprising: in response to a request to make a three-point turn for anautonomous driving vehicle (ADV), generating a forward turning pathusing a first spiral function based on a maximum forward curvaturechange rate associated with the ADV, wherein the forward turning path isinitiated based on a current vehicle status of the ADV, whereincoordinates (x, y) of any given point along the forward turning path iswithin a lane boundary of a current lane based on perception informationperceiving a driving environment surrounding the ADV; generating abackward turning path using a second spiral function based on a maximumbackward curvature change rate associated with the ADV, wherein thebackward turning path is initiated from an end point of the forwardturning path; generating a three-point turn path based on the forwardturning path and the backward turning path; and issuing one or morecontrol commands to control the ADV to drive according to thethree-point turn path.
 10. The non-transitory machine-readable medium ofclaim 9, wherein the first spiral function is configured such that, foreach of a plurality of points along the forward turning path, a headingdirection (θ) is determined based on an initial heading direction (a)and an initial curvature (b) of the ADV at a starting point of theforward turning path.
 11. The non-transitory machine-readable medium ofclaim 10, wherein the heading direction (θ) is determined further basedon a distance (s) between each point and the starting point and amaximum curvature change rate (c) of the ADV.
 12. The non-transitorymachine-readable medium of claim 11, wherein the heading direction (θ)of a given point is determined according to following equation:θ=a+b*s+c*s²/2.
 13. The non-transitory machine-readable medium of claim12, wherein a curvature represented by a derivative of the headingdirection (dθ) of any given point is less than a maximum curvatureassociated with the ADV.
 14. The non-transitory machine-readable mediumof claim 11, wherein coordinates (x, y) of a given point along theforward turning path are based on following equations: x=∫₀ ^(s) cos(θ)ds+x₀ and y=∫₀ ^(s) sin(θ) ds+y₀, wherein coordinate (x₀, y₀) representsan initial location of the ADV at the starting point of the firstforward turning path.
 15. A data processing system, comprising: aprocessor; and a memory coupled to the processor to store instructions,which when executed by the processor, cause the processor to performoperations, the operations including in response to a request to make athree-point turn for an autonomous driving vehicle (ADV), generating aforward turning path using a first spiral function based on a maximumforward curvature change rate associated with the ADV, wherein theforward turning path is initiated based on a current vehicle status ofthe ADV, wherein coordinates (x, y) of any given point along the forwardturning path is within a lane boundary of a current lane based onperception information perceiving a driving environment surrounding theADV, generating a backward turning path using a second spiral functionbased on a maximum backward curvature change rate associated with theADV, wherein the backward turning path is initiated from an end point ofthe forward turning path, generating a three-point turn path based onthe forward turning path and the backward turning path, and issuing oneor more control commands to control the ADV to drive according to thethree-point turn path.
 16. The data processing system of claim 15,wherein the first spiral function is configured such that, for each of aplurality of points along the forward turning path, a heading direction(θ) is determined based on an initial heading direction (a) and aninitial curvature (b) of the ADV at a starting point of the forwardturning path.
 17. The data processing system of claim 16, wherein theheading direction (θ) is determined further based on a distance (s)between each point and the starting point and a maximum curvature changerate (c) of the ADV.
 18. The data processing system of claim 17, whereinthe heading direction (θ) of a given point is determined according tofollowing equation: θ=a+b*s+c*s²/2.
 19. The data processing system ofclaim 18, wherein a curvature represented by a derivative of the headingdirection (dθ) of any given point is less than a maximum curvatureassociated with the ADV.